As a technique according to related art for stabilizing an image in an image processing apparatus, there is a technique for discharging toner which is deteriorated over time (toner refresh) and supplying new toner, thereby satisfactorily maintaining developing conditions. In this technique, the image processing apparatus forms a high-density band-like pattern of each color on the entire surface of a transfer belt in an image-formable range in a main-scanning direction, thereby discharging the deteriorated toner (hereinafter, this control is referred to as control A).
In addition, as another technique for stabilizing an image in an image processing apparatus, there is a technique for correcting toner density (the color density of a formed image). In this technique, the image processing apparatus forms particular high-density and low-density (halftone) patterns of each color on the transfer belt, reads the density of toner attached at this time using a sensor, and feeds back the result to a control unit for image formation, thereby correcting the toner density (hereinafter, this control is referred to as control B).
However, these controls take time, and since the print job of a user is not executed while these controls are performed, the user has to wait.